I am very new to cpanel, however have recently taken responsibility of a server using cpanel to manage it. I am trying to change the passwords via the WHM List Accounts feature and getting the message above. Is there anything I can try or look for?

Could you let us know the output to /usr/local/cpanel/logs/error_log when you notice this error message? Ensure you post the output in CODE tags, and only post the output that appears when the error message is generated in the interface. EX:

Thanks again for your response. Sadly the issue is fixed now - I say sadly as soon after posting my question my production hard drive failed and I had to rebuild on new hardware. Pretty much the worst possible solution but the change password problem is no longer an issue!

To update, it looks like this issue stemmed from a read-only mount of the primary partition "/". The advice in the support ticket was to remount the partition with "read-write" permissions instead of "read-only" permissions.